The present invention relates to a process for the continuous production of an extruded section, in particular a section made of aluminum or an aluminum alloy, in which a previously fabricated rod is introduced to and pressed through a die by means of a friction wheel.
A process for the continuous production of extruded sections is known under the name CONFORM. In that process, metal in the form of granules, pre-extruded bar or cast rod (Properzi rod) serving as starting materials is introduced into the groove of a friction wheel then pressed through a die. The above-mentioned starting materials, however, exhibit certain disadvantages.
Pre-extruded bar material normally ensures a good quality product. The costs, however, are high as a preliminary extrusion step must be performed prior to the conform process. Furthermore, such rod is normally not coiled so that it is difficult to introduce the rod into the groove of the friction wheel.
Properzi rod can usually be produced free of defects only with pure aluminum and dilute aluminum alloys. Further, such rod normally features structural defects such as, for example, central porosity or non-uniform cell structure.
The use of conventionally cast rods of higher alloyed materials leads to problems of quality as these rods normally feature an approximately 1 cm thick segregation zone at the surface which builds up in the friction wheel and leads to segregate entering the extrusion.
In the case of another known continuous process liquid metal is poured into the groove of a cooled friction wheel and the solidified metal is subsequently extruded through a die. In this so called CASTEX casting process, the solidification takes place in the groove of the cooled friction wheel. The solidification conditions are comparable with those noted above with regard to Properzi rod and, consequently similar problems relating to casting and structural inhomogenity are experienced. Furthermore, the peripheral shell solidifying in contact with the groove is subjected to mechanical deformation as a result of the braking action of the backer block. This leads to further structural inhomogenities, for example, segregation effects which appear in the product which are a detriment to product quality. In general, the process is not sufficiently developed for commerical application to higher alloyed materials.
Accordingly, it is principle, the object of the present invention to produce extruded sections using a friction wheel wherein the sections are of high quality and economic to produce. In order to accomplish the foregoing an appropriately shaped intermediate product is produced as the starting material for extrusion and introduced in the solidified state into the friction wheel.